1. Field of the Invention
The present invention relates to an air conditioner, especially, it relates to a material used for forming a heat exchanger and a baseboard of an outdoor unit.
2. Description of the Related Art
An outer chassis of the outdoor unit of a conventional air conditioner should be coated for maintaining a corrosion resistance property and protecting a design. In addition to that, when manufacturing the outer chassis, before pressing, there is a need for performing an anti-corrosive process and an oiling process for a steel board being used as the material. There is an issue of necessity of the extra process of washing the anti-corrosive agent and the oil, after finishing the sheet metal processing, and before coating it.
Moreover, since the outer chassis of the outdoor unit of the conventional air conditioner is coated after the pressing and welding, it faces a problem of rust occurrence from a portion out of reach by a coating material.
Further, the outer chassis of the outdoor unit of the conventional air conditioner has the following problem. That is, it was impossible to implement the resistance spot welding on a pre-coated steel board in case of pressing the pre-coated steel board, because an electrical property of the pre-coated steel board deteriorates prominently.
Furthermore, when a sunlight directly hits the outer chassis of the outdoor unit of the conventional air conditioner, an interior of the outdoor unit becomes high in temperature due to a poor light reflectance of the outer chassis, so it faces a problem of reduction in the efficiency of the cooling operation.
The patent document 1 discusses an outer casing of the outdoor unit of the air conditioner that can maintain an excellent corrosion resistance property and protect the design equal or superior to the conventional air conditioner without coating. The outer chassis of the outdoor unit of the air conditioner comprises a casing manufactured without the coating for storing the mechanical and electrical components of the air conditioner, and a highly durable alloy plated steel that is coated by resin of a prescribed thickness on its surface, including zinc and aluminum components within a composition of the plated steel, that is used on the steel board for press molding at least a portion of the chassis. The highly durable alloy plated steel has an r-value (the plastic strain ratio=Lankford value) of 1.6 or more with an elongation value of 40% and more derived from the tensile test, for allowing an oil-free press molding process. In addition to that, the highly durable alloy plated steel has a coefficient of dynamic friction of the film coated surface which is not more than 0.17.
According to the outer casing of the outdoor unit of the air conditioner of the patent document 1, the plated portions have a good durability, and it can protect the design to the same extent as the sheet metal components that are coated. However, a steel base becomes exposed at a cut section of the sheet metal. There is a limitation in restraining occurrence of the rusts entirely. For example, the patent document 2 discusses the air conditioner that constructs external components of the air conditioner and inner components that directly contact the drain water, with a highly corrosion resistant hot-dipped Zn—Al—Mg plated steel board. This air conditioner forms a protective film on the exposed portions of the steel base. The corrosion of the steel base is prevented by formation of this coated film.    [Patent document 1] Japanese Patent No. 3702870    [Patent document 2] Japanese Published Patent Application No. 2004-69161